Hydrogen gas storing device

ABSTRACT

A plurality of MH tank modules ( 13 ) each include a cylindrical porous member ( 14 ). The porous member ( 14 ) is formed as a hydrogen flow path ( 15 ) through which hydrogen can flow and has straight grooves formed on the outer circumferential surface. A plurality of fins ( 17 ) are attached to the porous member ( 14 ). A first edge and a second edge of each fin ( 17 ) are fitted in different grooves. The fins ( 17 ) define a plurality of accommodation chambers ( 19 ) for accommodating MH powder P. The MH tank modules ( 13 ) are accommodated in the housing while being arranged adjacent to each other to form a predetermined shape. Heat medium pipes ( 22   a,    22   b ) are arranged in the housing ( 12 ) so as to contact the fins ( 17 ) and correspond to the accommodation chambers ( 19 ). Heat medium flows through the heat medium pipes ( 22   a,    2   b ). Therefore, it is possible to provide a hydrogen gas storing device that easily increases the number of places to be installed in and facilitates the installment.

TECHNICAL FIELD

The present invention relates to a hydrogen gas storing device.

BACKGROUND ART

As a hydrogen storage tank, there is known a technique in which powderedhydrogen absorbing metal (hereinafter, referred to as MH) isaccommodated in a tank, and MH absorbs and stores hydrogen, and releaseshydrogen to be utilized.

MH has a property of generating heat when storing hydrogen and aproperty of absorbing heat when releasing hydrogen. Each time MH storesand releases hydrogen, the MH generates or absorbs heat. Therefore, ahydrogen storage tank using MH may be provided with a function of a heatexchanger that heats and cools the MH.

As one example of a hydrogen storage tank that accommodates MH and has afunction as an heat exchanger, a heat exchanger incorporating metalhydride has been proposed, in which an inner space between a sealedcylinder and a hydrogen pipe therein is divided into a plurality ofsmall chambers with partitions, and each small chamber is filled withmetal hydride powder (refer to Patent Document 1). In the heat exchangerincorporating metal hydride disclosed in Patent Document 1, thepartitions defining the small chambers are formed by aluminum alloyplates and serve as heat-transfer plates. Since heat medium flows tocontact the outer circumferential surface of the sealed cylinder, heatexchange takes place between the heat medium and the powdered metalhydride through the sealed cylinder and the partitions.

Patent Document 1: Japanese Laid-Open Patent Publication No. 8-178463

DISCLOSURE OF THE INVENTION

However, when the heat exchanger incorporating metal hydride disclosedin Patent Document 1 is installed on, for example, an electric vehiclehaving a fuel cell, a space having desired shape and size cannot besecured at a planned installation position (for example, between theaxle of the rear wheels and the rear seats), and, in some cases, theheat exchanger cannot be installed. In this case, if the size of theheat exchanger is reduced, the single heat exchanger cannot provideperformance required for an electric vehicle having a fuel cell.Therefore, the heat exchanger incorporating metal hydride disclosed inPatent Document 1 has a disadvantage in that it can be installed in onlylimited locations.

Thus, heat exchangers of a reduced size may be prepared in a number thatsatisfies required performance of the vehicle, and the heat exchangersmay be arranged to form a desired shape. However, in this case, each ofthe heat exchangers needs to be fixed to the vehicle separately, whichmakes the installation of the heat exchangers troublesome.

Accordingly, it is an objective of the present invention to provide ahydrogen gas storing device that adds to the flexibility of installationand can be installed easily.

To achieve the foregoing objective and in accordance with a first aspectof the present invention, a hydrogen gas storing device including aplurality of tank modules, a housing, and a plurality of flow pathsthrough which heat medium flows is provided. The tank modules each havea cylindrical member and a plurality of fins. The cylindrical member hasa cylindrical wall, through which hydrogen can flow, and a plurality ofstraight grooves formed on the outer circumferential surface. The finsare attached to the grooves of the cylindrical member. One edge andanother edge of each fin are attached to the grooves of the cylindricalmember so that a plurality of accommodation chambers for accommodatinghydrogen absorbing metal are defined. The housing accommodates the tankmodules such that the tank modules are adjacent to each other and form apredetermined shape. Each flow path is arranged in the housing so as tobe correspond to one or more of the accommodation chambers whilecontacting one or more of the fins.

The “predetermined shape” refers to a shape that allows the hydrogen gasstoring device to be arranged in a space designed to receive the device.

According to this invention, a plurality of tank modules are adjacentlyarranged in the housing to form the predetermined shape. Thus, whenforming the hydrogen gas storing device, the tank modules can be freelyarranged to form a desired shape. Therefore, for example, even if adesired installation space cannot be secured, the shape of the housingcan be changed to conform to the existing installation space. Byadjacently arranging the tank modules in the housing, the outer shape ofthe hydrogen gas storing device can be adjusted to conform to theinstallation space. Thus, the device can be installed in a position inwhich a conventional device cannot be easily installed. This adds to theflexibility of installation.

A plurality of tank modules are accommodated in the housing. Thus, wheninstalling the device in an electric vehicle having a fuel cell, thedevice can be installed simply by fixing the housing to the vehicle.Therefore, compared to the case where a plurality of tank modules areseparately fixed, the hydrogen gas storing device is easily installed.

It is preferable that at least one of the flow paths be located betweentwo or more of the tank modules. In this case, a single flow path isconfigured to contact at least two fins, and it is possible to heat andcool hydrogen absorbing metal filling at least two accommodationchambers with heat medium flowing through a single flow path. Therefore,compared to the case where a flow path through which heat medium flowsis provided for each accommodation chamber, the number of the flow pathscan be reduced.

It is preferable that the flow paths extend in a direction parallel withthe axial direction of the cylindrical members. In this case, forexample, if the longitudinal direction of the fins is parallel with theaxial direction of the cylindrical portions, the flow paths can beconstructed to extend over the entire length of the fin. This allows theheat medium to perform heat exchange with the hydrogen absorbing metalover the entire length of the fins. Therefore, compared to the casewhere flow paths extend in a direction intersecting the axial directionof cylindrical members, the heat-transfer efficiency between heat mediumand hydrogen absorbing metal is improved.

It is preferable that at least one of the flow paths be arranged tocontact two or more of the fins.

In this case, it is possible to heat and cool hydrogen absorbing metalaccommodated in at least two accommodation chambers with heat mediumflowing through a single flow path. Therefore, compared to the casewhere a flow path through which heat medium flows is provided for eachaccommodation chamber, the number of the flow paths can be reduced.

It is preferable that a cross section of each tank module taken along adirection perpendicular to the center axis of the cylindrical member beshaped as a polygon, and that at least one of the flow paths be locatedat a position that corresponds to corners of two or more tank modules.

The “polygonal shape” includes not only a shape in which each corner isformed by two straight sides, but also a shape in which two straightsides are continuous with a curve in between, that is a shape having acurve at each corner.

In this case, compared to the case where a flow path through which heatmedium flows is provided for each accommodation chamber, the number ofthe flow paths can be reduced.

It is preferable that the flow paths include a flow path through whichheat medium flows in a direction from a first end toward a second end ofthe tank modules, and a flow path through which heat medium flows in adirection from the second end toward the first end of the tank modules.

Since the heat medium at the outlets of the flow paths has alreadyperformed heat exchange with the hydrogen absorbing metal, thetemperature of the heat medium at the outlets of the flow paths isdifferent from the temperature of the heat medium at the inlets of theflow paths. Therefore, since the temperature of the heat medium variesdepending on the positions in the flow, the temperature of the hydrogenabsorbing metal is uneven in some parts of the accommodation chamber ifthe heat medium flows in one direction.

However, in this preferred embodiment, a plurality of flow paths includeflow paths in which heat medium flows from the first ends to the secondends of the tank modules and flow paths in which heat medium flows fromthe second ends to the first ends of the tank modules. This reduces thetemperature difference between the hydrogen absorbing metal in the firstends of the tank modules and the hydrogen absorbing metal in the secondends of the tank modules.

It is preferable that each fin be bent to include a pair of partitionportions that extend toward the corresponding cylindrical member and anouter wall portion that is continuous to the partition portions, oneedge and another edge of the fin being attached to different grooves soas to one of the accommodation chambers, and that, in a state where thefins are attached to the cylindrical members, the outer wall portionsfunction as outer walls of the tank modules.

In a case where an outer wall is provided about each tank module inaddition to the fins, the fins and the outer walls need to be installedwhen assembling the tank modules. In this configuration, the fins areformed by bending, and each single fin is used to define oneaccommodation chamber. An outer wall portion, which is a part of eachfin, is a used as the outer wall of a tank module. Therefore, nooperation for attaching the fins to the outer walls is required.Compared to the case where outer walls separate from fins are provided,the assembly of the tank module is easy.

It is preferable that each fin have in its part a curved portionprojecting into the corresponding accommodation chamber.

In this case, the curved portions reinforce the fins so that the finshave an increased strength against forces in a direction opposite to thedirection of the recess. Therefore, even if the hydrogen absorbing metalfilling the accommodation chambers is thermally expanded when absorbinghydrogen, and an outward force acts on the fins, the fins are preventedfrom being damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a hydrogen gasstoring device according to a preferred embodiment;

FIG. 2 is a perspective view illustrating an MH tank module;

FIG. 3 is a cross-sectional view taken along line 3-3, illustrating thehydrogen gas storing device shown in FIG. 1;

FIG. 4 is a cross-sectional view taken along line 4-4, illustrating thehydrogen gas storing device shown in FIG. 1;

FIG. 5 is a schematic cross-sectional view illustrating a hydrogen gasstoring device according to another embodiment;

FIG. 6 is a perspective view illustrating an MH tank module according toanother embodiment; and

FIG. 7 is a schematic view as viewed in an axial direction of porousmembers, illustrating a hydrogen gas storing device according to anotherembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described withreference to FIGS. 1 to 4.

As shown in FIG. 1, a hydrogen gas storing device 11 includes asubstantially rectangular box-shaped housing 12 (which is, for example,made of aluminum). A plurality of (six in the present embodiment) of MHtank modules 13, serving as tank modules, are arranged in the housing12. Specifically, the MH tank modules 13 are arranged adjacent to eachother to form a substantially quadrangular prism shape. In the housing12, the MH tank modules 13 are stacked to form multiple stages. Thehousing 12 has such a strength that it sufficiently withstands an innerpressure of a predetermined value (for example, 10 MPa) when the MH tankmodules 13 are fully filled with hydrogen.

As shown in FIG. 2, each MH tank module 13 has a porous member 14, whichserves as a cylindrical member formed of a porous material, at thecenter. The cross section of the MH tank module 13 taken along adirection perpendicular to the center axis of the porous member 14 isrectangular.

Each porous member 14 includes a cylindrical wall 14 a, through whichhydrogen flows (permeates), and a hydrogen flow path 15, which extendsover the entire length of the MH tank module 13. Each porous member 14has a plurality of (eight in the present embodiment) straight grooves16, which are formed on the outer circumferential surface and extendalong the center axis of the porous member 14.

The grooves 16 are arranged at equal intervals in the circumferentialdirection of the porous member 14. Each groove 16 has a width that isslightly greater than the thickness of two fins 17. Each groove 16receives a first edge 18 a of one of the fins 17 and a second edge 18 bof an adjacent fin 17.

The fins 17 are formed by aluminum alloy plates, and are bent to be inthe shape of a right triangle. Each fin 17 extends along the axialdirection of the porous member 14 and is attached to the outercircumference of the porous member 14 by fitting one edge, or the firstedge 18 a, and the other edge, or the second edge 18 b, into differentgrooves 16. When attached to the porous member 14, each fin 17 definesan accommodation chamber 19, which accommodates MH powder P. The fins 17are attached to the porous member 14 with their longitudinal directionbeing parallel with the axial direction of the porous member 14, and aplurality of accommodation chambers 19 are formed in the MH tank module13.

Spaces between the porous member 14 and each first edge 18 a and eachsecond edge 18 b of the fins 17 are sealed, so that the MH powder P doesnot leak to the outside through the grooves 16. The MH powder P in eachaccommodation chamber 19 contacts the outer circumferential surface ofthe porous member 14. The MH tank module 13 shown in FIG. 2 has no MHpowder P accommodated therein.

Each fin 17 is bent to include a pair of partition portions 23 extendingtoward the center of the MH tank module 13 and an outer wall portion 20that is continuous to the pair of partition portions 23. The partitionportions 23 extend from the sides of the outer wall portion 20 andprevent precipitation of the MH powder P.

With a plurality of the fins 17 attached to each porous member 14, theouter walls 20 also function as the outer walls of the MH tank module13. In view of the space efficiency and thermal efficiency, adjacentfins 17 preferably contact each other.

Part of each outer wall portion 20 is bent so that a curved portion 21is formed. The curved portion 21 projects into the accommodation chamber19. The curved portions 21 are each formed such that its recess isslightly greater than half the outer circumference of heat medium pipes22 a, 22 b. In portions that do not face the housing 12, two curvedportions 21 face each other to form a piping space, into which one ofthe heat medium pipes 22 a, 22 b (see FIG. 1) is inserted.

As shown in FIGS. 2 to 4, an end wall 13 a is welded to each of the ends(first end and second end) of each MH tank module 13 in the longitudinaldirection, so that the openings of the accommodation chambers 19 in thelongitudinal direction are closed. A pipe 24 is provided at one of theend walls 13 a that forms a first end of each MH tank module 13. Thepipe 24 communicates with the flow path 15 of the porous member 14 whenattached to the MH tank module 13. At positions of each accommodationchamber 19 that corresponds to one of the end walls 13 a, an injectionhole and a plug for closing the injection hole (neither is shown) areprovided. The MH powder P is introduced into each accommodation chamber19 through the injection hole.

As shown in FIG. 1, the housing 12 includes a main body 25 having arectangular cross section. The main body 25 has on the inner surfacepipe recesses 25 a for receiving half of each heat medium pipe 22 a, 22b. With the MH tank modules 13 accommodated, the curved portions 21 ofthe fins 17 face the pipe recesses 25 a, so that piping spaces forreceiving the heat medium pipes 22 b are formed. As shown in FIG. 3, arectangular inlet header 27 with a bottom is attached to the main body25 to face a first open end 26 of the main body 25. The inlet header 27supplies heat medium (such as water, oil, and engine coolant) to theheat medium pipes 22 a, 22 b.

The inlet header 27 is installed by welding its open end to the firstopen end 26 of the main body 25. The interior of the inlet head 27 isconnected to a heat medium tank (not shown) with a pipe and serves as aheat medium supply chamber 28. As shown in FIG. 4, pipe insertion holes29 for receiving the pipes 24 are formed in the bottom of the inletheader 27. The number of the pipe insertion holes 29 is the same as thenumber of the MH tank modules 13. The gap between the open end of theinlet header 27 and the first open end 26 of the main body 25 is sealedto prevent heat medium from leaking.

On the opposite side of the main body 25 with respect to the inletheader 27, an outlet header 30 is provided. After performing heatexchange with the MH powder P, the heat medium is discharged to theoutlet header 30. The outlet header 30 has a rectangular shape and abottom. The outlet header 30 is fixed to a second open end 31 of themain body 25 by welding. With the outlet header 30 fixed to the secondopen end 31 of the main body 25, the interior of the outlet header 30serves as a discharge chamber 32, which is connected to the heat mediumtank with a pipe (neither is shown). After flowing through the heatmedium pipes 22 a, 22 b, the heat medium flows into the dischargechamber 32.

All the heat medium pipes 22 a, 22 b extend parallel with axialdirection of the porous members 14, and their inlet ends 33 extend intothe supply chamber 28. Outlet ends 34 of the heat medium pipes 22 a, 22b extend into the discharge chamber 32. As shown in FIG. 1, the heatmedium pipes 22 a, 22 b are each arranged in a piping space andcorrespond to at least one of the accommodation chambers 19. Of the heatmedium pipes 22 a, 22 b, each of the heat medium pipes 22 a that arelocated between MH tank modules 13 contacts two fins 17 and correspondsto two accommodation chambers 19. Of the heat medium pipes 22 a, 22 b,each of the heat medium pipes 22 a that are located between an MH tankmodules 13 and the main body 25 contacts a fin 17 and corresponds to oneaccommodation chamber 19. The heat medium flows only in one direction.In the preset embodiment, the heat medium flows through the heat mediumtank, the supply chamber 28, the heat medium pipes 22 a, 22 b, thedischarge chamber 32, and the heat medium tank, in this order.

A method for assembling the hydrogen gas storing device 11 will now bedescribed.

First, the main body 25 is prepared, and a plurality of the MH tankmodules 13 are sequentially arranged from the lower row through theopening. At this time, the MH tank modules 13 are arranged such that thecurved portions 21 of the fins 17 face the pipe recesses 25 a of themain body 25. Accordingly, each pair of the curved portions 21 and eachpair of a pipe recess 25 a and the corresponding curved portion 21defines a piping space. Next, the heat medium pipes 22 a, 22 b areinserted into the piping spaces in the main body 25. With the inlet ends33 arranged outside from the first open end 26, the outlet ends 34 ofthe heat medium pipes 22 a, 22 b are arranged outside of the second openend 31. This procedure is repeated until all the piping spaces receivethe heat medium pipes 22 a, 22 b. Then, the inlet header 27 and theoutlet header 30 are fixed to the main body 25 through welding toassemble the housing 12. The inlet header 27 is fixed to the main body25 with the pipes 24 inserted in the pipe insertion holes 29 andextending to the outside.

An operation of the hydrogen gas storing device 11 thus constructed willnow be described.

In a case where the hydrogen gas storing device 11 is installed, forexample, in an electric vehicle with a fuel cell, and hydrogen isdirectly used as fuel, consumption of hydrogen at the fuel electrodescauses each MH tank module 13 to release hydrogen, which is in turnsupplied to the fuel electrodes through the pipes 24. When hydrogen isreleased from each MH tank module 13, reaction that occurs in the MHpowder P is shifted to hydrogen release reaction between hydrogenstorage and release reactions, which causes the MH powder P to releasehydrogen. Since the release of hydrogen is an endothermic reaction, ifheat required for releasing hydrogen is not supplied by the heatingmedium, the MH powder P releases hydrogen by using sensible heat, whichcauses the temperature of the MH powder P to drop. However, since heatmedium of a predetermined temperature is supplied to the supply chamber28 of the inlet header 27, and flows through the heat medium pipes 22 a,22 b, the heat medium heats the MH powder P to a predeterminedtemperature through the fins 17. Accordingly, the reaction of hydrogenrelease smoothly progresses.

Then, the MH powder P in the accommodation chambers 19 releases hydrogeninto the MH tank modules 13 along the entire length of the MH tankmodules 13. Since the MH powder P in the accommodation chambers 19contacts the outer circumferential surface of the porous members 14along the entire length of the porous members 14, the released hydrogenreaches the hydrogen flow paths 15 through minute holes of thecylindrical walls 14 a. The hydrogen is then released to the outside ofthe hydrogen gas storing device 11 through the pipes 24 of the MH tankmodules 13 and is supplied to the fuel electrodes. The temperature ofthe MH powder P is maintained to a temperature that allows the releasereaction of hydrogen to smoothly progress by adjusting the temperatureor the flow rate of the heating medium, and the release of hydrogen isefficiently executed so that the amount of hydrogen corresponding to theamount required by the fuel cell is released.

When filling the hydrogen gas storing device 11 with hydrogen afterhydrogen has been released therefrom, that is, when causing the MHpowder P to absorb hydrogen, hydrogen is caused to flow into thehydrogen flow paths 15 of the porous members 14 from the pipes 24. Thehydrogen that has flowed into the hydrogen flow paths 15 is diffusedwhile flowing along the entire length of the MH tank modules 13. Then,the hydrogen reacts with the MH powder P, which is present over theentire length of the MH tank modules 13 in the accommodation chambers19, to become hydride and be stored in the MH powder P. The supply ofhydrogen to the MH powder P is continued until the interior of each MHtank module 13 reaches a predetermined pressure (for example, 10 MPa).Even if repetitive storing and release of hydrogen pulverizes the MHpowder P, the pulverized MH powder P is prevented from leaking to theoutside of the MH tank modules 13 because the porous members 14 have afunction as filters to the MH powder P.

Since the storage reaction of hydrogen is an exothermic reaction, thestorage reaction of the hydrogen is hampered unless the heat generatedby the reaction is removed. However, when charging hydrogen, lowtemperature heating medium is supplied to the supply chamber 28 of theinlet header 27 and flows into the heat medium pipes 22 a, 22 b, theheat generated in the MH powder P is absorbed by the heating mediumthrough the fins 17 and carried out of the hydrogen gas storing device11. Therefore, the temperature of the MH powder P is maintained to atemperature that permits a smooth storing reaction of hydrogen, so thatthe hydrogen is efficiently stored.

Also, in the electric vehicle having a fuel cell, the hydrogen gasstoring device 11 is installed between the axle of the rear wheels andthe rear seat. The hydrogen gas storing device 11 of the presentinvention is configured by arranging three MH tank modules 13 adjacentto each other, and stacking another set of three MH tank modules 13 overthe first three MH tank modules 13, so that the device 11 has aquadrangular prism shape. Therefore, while maintaining the performanceof the conventional product, the hydrogen gas storing device 11 has aless height than the conventional product while having a greater width.The device 11 thus can be arranged between the rear wheel axle and therear seat.

When installing the hydrogen gas storing device 11 between the rearwheel axle and the rear seat, the housing 12 is fixed using brackets(not shown), so that the multiple MH tank modules 13 can besimultaneously fixed. Therefore, for example, compared to a case wherethe MH tank modules 13 are separately fixed using a bracket, theinstallation is facilitated.

This embodiment provides the following advantages.

(1) The multiple MH tank modules 13 are arranged adjacent to each otherto form a predetermined shape when being arranged in the housing 12.Therefore, when designing the hydrogen gas storing device 11, the shapecan be made to correspond to the installation space between the rearwheel axle and the rear seat. Thus, the device 11 can be installed in aplace where a conventional product cannot be placed. This adds to theflexibility of design.

(2) The hydrogen gas storing device 11 is configured such that themultiple MH tank modules 13 are adjacent to each other. Therefore, forexample, when the device 11 is installed in an electric vehicle with afuel cell, the MH tank modules 13 are easily fixed in the vehiclecompared to a case where multiple MH tank modules 13 are separatelyfixed. The hydrogen gas storing device 11 is therefore easily installed.

(3) The first edge 18 a and the second edge 18 b of each fin 17 arefitted in the grooves 16 on the outer circumferential surface of theporous member 14, so that the fins 17 are attached to the porous member14. The fins 17 define the accommodation chambers 19 for accommodatingthe MH powder P. Therefore, unlike a case where each MH tank module 13only has a single accommodation chamber 19, each MH tank module 13 hassegmented accommodation chambers 19. This increases the area at whichthe MH powder P and the fins 17 contact each other. Thus, heat exchangebetween the MH powder P and the heating medium through the fins 17 isefficiently performed.

(4) Each porous member 14 has a cylindrical wall 14 a and a hydrogenflow path 15 extending along the entire length of the MH tank module 13.The first edge 18 a and the second edge 18 b of each fin 17 are fittedin grooves 16 in the outer circumferential surface of the porous member14, so that the accommodation chambers 19 are defined by the fins 17.The hydrogen flow path 15 allows hydrogen to flow along the entirelength of the MH tank module 13 and to react with the MH powder P in theaccommodation chambers 19 through the cylindrical wall 14 a. Therefore,in the MH tank module 13, hydrogen is allowed to smoothly react with theMH powder P along the entire length.

(5) The heat medium pipes 22 a, 22 b pass through the housing 12, sothat the housing 12 does not intervene when heat exchange takes placebetween heat medium and the MH powder P. Thus, compared to a case wherethe heat medium pipes 22 a, 22 b are located outside of the housing 12,and heat exchange with the MH powder P takes place with the housing 12in between, the heat exchange between the heat medium and the MH powderP is efficiently performed.

(6) Among the heat medium pipes 22 a, 22 b, which function as flowpaths, each of the heat medium pipes 22 a located between MH tankmodules 13 contacts two fins 17, and heats and cools the MH powder P intwo accommodation chambers 19 using heat medium flowing through thesingle heat medium pipe 22 a. Therefore, compared to a case where heatpipes are separated from the accommodation chambers 19, the number ofthe heat medium pipes can be reduced.

(7) The heat medium pipes 22 a, 22 b extend parallel with the axialdirection of the porous members 14, and the fins 17 are attached withthe longitudinal direction being parallel with the axial direction ofthe porous members 14. This enlarges the area of the surfaces of theheat medium pipes 22 a, 22 b that contact the fins 17. Therefore, forexample, if the heat medium pipes 22 a, 22 b are configured to extendalong the entire length of the fins 17, heat medium is allowed toperform heat exchange with the MH powder P along the entire length withthe fins 17 in between. Thus compared to a case where heat medium pipesextend to intersect the axial direction of the porous members 14, theheat-transfer efficiency between the heat medium and the MH powder P isimproved.

(8) Each fin 17 is bent to have a pair of partition portions 23extending toward the center of the MH tank module 13 and an outer wallportion 20 that is continuous to the partition portions 23. The firstedge 18 a and the second edge 18 b of each fin 17 are attached todifferent grooves 16 and define an accommodation chamber 19, andmultiple outer wall portions 20 function as the outer walls of the MHtank module 13. In other words, each fin 17 defines a singleaccommodation chamber 19 and the outer wall portion 20 functions as anouter wall of the MH tank module 13. Unlike the case of an MH tankmodule in which an outer wall is provided separately from fins, aprocess for attaching fin to the outer wall is not required in the aboveembodiment. Therefore, compared to the assembly of the MH tank modulehaving an outer wall provided separately from fins, the assembly of theMH tank module 13, which includes the fins 17 and the outer walls, iseasy.

(9) A curved portion 21, which projects into the accommodation chamber19, is formed in the outer wall portion 20 of each fin 17. The curvedportion 21, which is formed to projects into the accommodation chambers19, increases the strength of the fin 17 against force acting in adirection away from the accommodation chamber 19 (outward direction).

Therefore, even if the MH powder P accommodated in the accommodationchambers 19 is expanded when absorbing hydrogen, and an outward forceacts on the fins 17, the fins 17 are prevented from being damaged.

(10) The flow paths through which heat medium flows are formed by theheat medium pipes 22 a, 22 b. Therefore, even if the fins 17 areconfigured to contact the flow paths through which heat medium flows, nosealing needs to be provided between the fins 17 and the paths.Therefore, the flow paths through which heat medium flows are easilyformed in the housing 12.

The present invention is not limited to the embodiment described above,but may be embodied as follows, for example.

As long as the heat medium pipes 22 a, 22 b serving as flow paths areprovided to correspond to the accommodation chambers 19, all the heatmedium pipes 22 a, 22 b may be formed continuously. For example, a heatmedium pipe that is repeatedly folded back at the first end and thesecond end of the MH tank modules 13 so as to meander may be provided.In this case, one continuous heat medium pipe form a plurality of flowpaths corresponding to each of the accommodation chambers 19 in thehousing.

The positions of the heat medium pipes 22 a, 22 b serving as flow pathsmay be changed. For example, as shown in FIG. 5, heat medium pipes 39 a,39 b, 39 c may be provided at the corners of the MH tank modules 13. Inthis case, each heat medium pipe 39 a, which is located at one of thefour corners of the main body 25 and corresponds to a corner of an MHtank module 13, contacts two of the fins 17. Heat medium flowing througheach heat medium pipe 39 a thus heats and cools the MH powder P in twoaccommodation chambers 19. Also, each heat medium pipe 39 b, which islocated between two MH tank modules 13 and the main body 25 andcorrespond to corners of the two MH tank modules 13, contacts four fins17. Heat medium flowing through each heat medium pipe 39 b thus heatsand cools the MH powder P in four accommodation chambers 19.

Also, each heat medium pipe 39 c, which is located between four MH tankmodules 13 and correspond to corners of the four MH tank modules 13,contacts eight fins 17. Heat medium flowing through each heat mediumpipe 39 c thus heats and cools the MH powder P in eight accommodationchambers 19. Therefore, compared to a case where one heat medium pipe isprovided for each accommodation chamber 19, the configuration of theheat medium pipes 39 a, 39 b, 39 c needs less number of heat mediumpipes to correspond to all the accommodation chambers 19. That is, thenumber of the heat medium pipes can be reduced without lowering theheating and cooling performance of the MH powder P.

If the cross-sectional shape of each MH tank module 13 taken along adirection perpendicular to the axis of the porous member 14 ispolygonal, the corners of the polygon are not limited to be defined bytwo straight sides. For example, each MH tank module 13 may have such across-sectional shape taken along a direction perpendicular to the axisof the porous member 14, that two straight sides are connected to eachother via a curve. That is, each corner may be rounded.

The cross-sectional shape of each MH tank module 13 taken along adirection perpendicular to the axis of the porous member 14 may bechanged. The cross-sectional shape of each MH tank module 13 taken alonga direction perpendicular to the axis of the porous member 14 may bechanged to a polygon, such as a triangle and a hexagon. Thecross-sectional shape of the porous member 14 of each MH tank module 13does not need to be polygonal, but may be circular like an MH tankmodule 40 shown in FIG. 6. In this case, the MH tank module 40 has aplurality of fins 41. The outer wall plate 42 of each fin 41 has anarcuate cross-sectional shape, which forms a part of the circular crosssection when the fins 41 are attached to the porous member 14.

In place of the heat medium pipes 22 a, 22 b, which extend parallel withthe axial direction of the porous members 14, heat medium pipes thatintersect the axial direction of the porous members 14 may be used. Forexample, a plurality of heat medium pipes that extend in a directionperpendicular to the axial direction of the porous members 14 may bearranged along the axial direction of the porous members 14 at equalintervals. In this case, each heat medium pipe extends through the mainbody 25 and passes the housing 12, such that the inlet end and outletend of each pipe extend to the outside of the housing 12. The inletheader 27 is attached to the outer circumferential surface of the mainbody 25, and the outlet header 30 is attached to the main body 25 on theside opposite to the inlet header 27. This structure allows heat mediumto flow through the heat medium tank, the supply chamber, the heatmedium pipes, the discharge chamber, and the heat medium tank insequence, so that the heat medium heats and cools the MH powder P.

Instead of heat medium pipes, piping spaces defined by the curvedportions 21 or by the pipe recesses 25 a and the curved portions 21 maybe used as flow paths through which heat medium flows. In this case, toensure the sealing of the flow paths, joint lines between contactingcurved portions 21 and joint lines between a curved portion 21 and apipe recess 25 a need to be sealed.

Heat medium that flows through the heat medium pipes 22 a, 22 b does notneed to flow only in one direction. For example, the heat medium pipes22 a, 22 b at the same height may include alternately arranged firstheat medium pipes and second heat medium pipes. Through each first heatmedium pipe, heat medium flows from the first end of the MH tank module13 (the end wall 13 a at which the pipes 24 are provided) to the secondend of the MH tank module 13 (the end wall 13 a at which no pipes 24 areprovided), and through each second heat medium pipe, heat medium flowsfrom the second end of the MH tank module 13 to the first end of the MHtank module 13. In this case, the housing is formed only by the mainbody 25. In addition to the housing, a first supply portionincorporating the inlet ends of the first heat medium pipes and a firstdischarge portion incorporating the outlet ends of the second heatmedium pipes are provided. On the opposite side of the housing to thefirst supply portion and the first discharge portion, a second dischargeportion incorporating the outlet ends of the first heat medium pipes anda second supply portion incorporating the inlet ends of the second heatmedium are provided. This configuration includes flow paths throughwhich heat medium flows from the first ends of the MH tank modules 13 tothe second ends, and flow path through which heat medium flows from thesecond ends of the MH tank modules to the first ends. This reduces thetemperature difference between the MH powder P in parts of the MH tankmodules 13 closer to the first ends and the MH powder in parts of the MHtank modules 13 closer to the second ends.

The outer shape of the hydrogen gas storing device 11 may be changed bychanging the shape of the housing 12. For example, in accordance withthe shape of a space in an electric vehicle, the housing 12 may beformed to have a staircase like shape as shown in FIG. 7 beforeaccommodating the MH tank modules 13 in the housing 12. Therefore, evenif the shape of a remaining space has a staircase like shape, thehydrogen gas storing device 11 can be installed in the electric vehicle.

The material of the housing 12 is not particularly limited as long asthe housing 12 has a sufficient strength that withstands a predeterminedpressure in the MH tank modules 13 (for example, 10 MPa) when the MHtank modules 13 is filled with hydrogen. For example, instead ofaluminum, the housing 12 may be formed of iron or fiber reinforcedplastic.

When the width of each groove 16 is wider than the combined width of thefirst edge 18 a and the second edge 18 b of the fin 17, and the firstedge 18 a and the second edge 18 b of the fin 17 cannot be firmly fittedinto the groove 16, the first edge 18 a and the second edge 18 b of thefin 17 may be attached to the groove 16 using adhesive after insertingthe first edge 18 a and the second edge 18 b into the groove 16.

The grooves 16 do not need to be formed to extend in a straight line aslong as each groove 16 is capable of receiving the first edge 18 a andthe second edge 18 b of fins 17. For example, if porous members havingwavy shapes are used, grooves on the outer surface of the porous membersextend along a wavy line, but not in a straight line.

The fins 17 with the curved portions 21 can be made by a method otherthan bending of parts of the outer wall portion 20. For example, it ispossible to form fins 17 with a curved portion 21 in the outer wallportions 20 by extrusion molding.

The hydrogen gas storing device 11 is not restricted to use in anelectric vehicle with a fuel cell, but may be employed in a hydrogensupply source of a hydrogen engine or a heat pump.

The heat medium pipes 22 a, 22 b do not need to extend in a straightline. For example, if the diameters of the heat medium pipes 22 a, 22 bremain the same, the pipes 22 a, 22 b have a greater area contacting thefins 17 when they have wavy shapes than when they are formed to extendin straight lines.

1. A hydrogen gas storing device comprising: a plurality of tank moduleseach having a cylindrical member and a plurality of fins, thecylindrical member having a cylindrical wall, through which hydrogen canflow, and a plurality of grooves formed on the outer circumferentialsurface, the fins being attached to the grooves of the cylindricalmember, wherein one edge and another edge of each fin are attached tothe grooves of the cylindrical member so that a plurality ofaccommodation chambers for accommodating hydrogen absorbing metal aredefined; a housing accommodating the tank modules such that the tankmodules are adjacent to each other and form a predetermined shape; and aplurality of flow paths through which heat medium flows, wherein eachflow path is arranged in the housing so as to be correspond to one ormore of the accommodation chambers while contacting one or more of thefins.
 2. The hydrogen gas storing device according to claim 1, whereinat least one of the flow paths is located between two or more of thetank modules.
 3. The hydrogen gas storing device according to claim 1,wherein the flow paths extend in a direction parallel with the axialdirection of the cylindrical members.
 4. The hydrogen gas storing deviceaccording to claim 1, wherein at least one of the flow paths is arrangedto contact two or more of the fins.
 5. The hydrogen gas storing deviceaccording to claim 1, wherein a cross section of each tank module takenalong a direction perpendicular to the center axis of the cylindricalmember is shaped as a polygon, and wherein at least one of the flowpaths is located at a position that corresponds to corners of two ormore tank modules.
 6. The hydrogen gas storing device according to claim1, wherein the flow paths include a flow path through which heat mediumflows in a direction from a first end toward a second end of the tankmodules, and a flow path through which heat medium flows in a directionfrom the second end toward the first end of the tank modules.
 7. Thehydrogen gas storing device according to claim 1, wherein each fin isbent to include a pair of partition portions that extend toward thecorresponding cylindrical member and an outer wall portion that iscontinuous to the partition portions, one edge and another edge of thefin being attached to different grooves so as to one of theaccommodation chambers, and wherein, in a state where the fins areattached to the cylindrical members, the outer wall portions function asouter walls of the tank modules.
 8. The hydrogen gas storing deviceaccording to claim 1, wherein each fin has in its part a curved portionprojecting into the corresponding accommodation chamber.